The invention pertains to the manufacture of a stent carrying balloon catheter having a predetermined arrangement of differentially lubricious areas on the balloon catheter to prevent unexpected movement of the stent when in situ in the body and to insure precise stent deployment.
This invention relates to stent carrying balloon catheters, sometimes referred to as dilatation catheters, for use in angioplasty and other various vessel repair procedures. Angioplasty has become recognized as an efficient and effective method of opening stenoses in the vascular system. In the most widely used form of angioplasty, a balloon catheter is guided through the vascular system until the balloon, which is carried at the distal end of a catheter shaft, and which may carry an expandable stent, is positioned across the stenosis or lesion, i.e., vessel obstruction. The balloon is then inflated to apply pressure to the obstruction which is essentially remolded by pressing it against the inner wall of the vessel whereby the vessel is opened for improved flow. Due the expansion of the balloon, the stent, which is situated on the balloon, is also expanded and released to aid in support and/or repair of the vessel wall.
Balloon catheters are of various types. One type is fed over a guide wire (i.e., xe2x80x9cover-the-wirexe2x80x9d catheters) and another type serves as its own guide wire (i.e., xe2x80x9cfixed-wirexe2x80x9d catheters). Variations of these two basic types also have been developed such as the so called xe2x80x9crapid exchangexe2x80x9d type, xe2x80x9cinnerlessxe2x80x9d catheters, and others. As used herein, the term xe2x80x9cballoon catheterxe2x80x9d is meant to include all of the various types of angioplasty catheters which carry a balloon for performing angioplasty and any other type of stent carrying balloon catheter. Balloon catheters may also be of a wide variety of inner structure, such as different lumen design, of which there are at least three basic types: triple lumen, dual lumen and co-axial lumen. All varieties of internal structure and design variation are meant to be included by use of the term xe2x80x9cballoon catheterxe2x80x9d herein.
When used in percutaneous transluminal coronary angioplasty (PTCA), the balloon catheter is typically advanced through a guide catheter to a preselected vessel location, such as the aorta, for example. Using fluoroscopy, the surgeon manipulates the catheter until the balloon is located across the stenosis or obstruction. As already pointed out, this may involve the use of a guide wire over which the catheter is moved or alternatively the catheter may act as its own guide wire, depending on the particular design. The manipulation of the stent carrying balloon catheter through the guide catheter and through the vessels to the obstruction requires the balloon catheter to have a number of different features.
One such feature is the use of a lubricious coating over the exterior surfaces of the catheter and balloon to facilitate movement of the catheter through the sometimes tortuous paths within the vascular system to the preselected vessel location for performing the angioplasty. A wide variety of such lubricious coatings have become commonplace for use with respect to catheters and other devices which are insertable into the body in connection with surgical procedures and the like. All such coatings are intended to be included herein with respect to the use of the term xe2x80x9clubricious coatingxe2x80x9d. Examples of such coatings include silicone and most preferably hydrophilic coatings involving hydrogel polymers or the like, such as polymer networks of a vinyl polymer and an uncrosslinked hydrogel, for example. Polyethylene oxide (PEO) is a preferred hydrogel. A preferred vinyl polymer is neopentyl glycol diacrylate (NPG). Such compositions are more fully disclosed in co-pending U.S. patent application, Ser. No. 07/809,889 which is assigned to the same assignee as is the present invention and which is incorporated herein by reference.
These coatings have even been known to include certain agents such as drugs which may be permanently entrapped in the coating or leachable therefrom into the body. For example, heparin has been used in such a fashion. Heparin is well known as an agent which is often used to inhibit clot formation in the blood. Again, the term xe2x80x9clubricious coatingxe2x80x9d is meant to include all such variations.
One problem with a stent carrying balloon catheter having a lubricious coating is that during location and release of the carried stent, the stent tends to slip off the balloon due to the lubricious coating on the balloon. Coating both the shaft and balloon of the catheter inhibits the doctor""s ability to locate, activate and deploy stents at any particular lesion. The stent is sometimes worked off the balloon portion during the insertion of the catheter and during the expansion of the balloon. This unexpected movement of the stent might be regarded negatively by a surgeon. The present invention provides for more secure connection between the balloon and the stent to prevent such slippage. Thus, though high lubricity is desirable for general movement, it is also desirable to provide a means of anchoring or positioning the stent in a fixed location on the balloon so as to avoid unexpected movement thereof upon the balloon during positioning and expansion.
The invention is a stent delivery catheter which has a lubricious coating on the shaft and, either, partial or no lubricious coating or an adhesive coating, or a combination thereof on the balloon. The lubricious coating, which is preferably hydrophilic, provides lubricity to the catheter while the uncoated or partially coated or adhesive coated balloon is able to retain the stent during positioning and release without concern for coating induced slippage. This is accomplished by the present invention through the selective arrangement of lubricious and/or adhesive coatings on the balloon catheter in which at least a portion of the balloon body is uncoated or less slippery or tacky while a relatively more lubricious coating is placed on at least a substantial portion of the catheter shaft extending in a proximal direction from the balloon toward the proximal end of the catheter shaft.
Generally then, the invention contemplates an improvement in the arrangement of lubricious coating(s) and/or adhesive coating(s) on the catheter to avoid stent slippage and to better anchor the stent in position for performing angioplasty or other vessel repair. This is accomplished by what may be termed herein as xe2x80x9cdifferential coatingxe2x80x9d or xe2x80x9cselective lubricatingxe2x80x9d. By this is meant that the lubricious properties of the catheter are selectively designed or constructed and arranged in a predetermined manner such that the catheter shaft i.e, substantially all of the catheter generally exhibits more lubricity than the balloon generally. In short, the catheter is more slippery than the balloon, relatively speaking. It can be seen that an important feature of the invention lies in the uncoated or less slippery balloon or portion thereof relative to the rest of the catheter so that the stent is more controllable.
Such an arrangement may be accomplished in a number of different ways. For example, in one embodiment, a lubricious coating may be provided over substantially the entire catheter, except for the balloon per se. In this embodiment, the balloon does not include any lubricious coating at all. The stent, which is placed over the balloon, is therefore not susceptible to slippage due to the greater coefficient of friction than a balloon with lubricant might have.
The balloon also may be coated partially or with a less lubricious or less slippery coating than the coating covering the shaft of the catheter. In such an instance, two different coatings may be used, such as a PEO composition as aforementioned on the catheter shaft and so forth, while a silicone coating is placed on the balloon per se. The balloon may also have specific areas coated, while leaving others uncovered to provide suitable contact with the stent.
In another variation, different compositions of PEO may be used on the shaft and balloon. In the PEO compositions aforementioned, comprised of PEO and NPG in isopropyl alcohol and water, variations in the amount of PEO content affect the final lubricity of the composition; the higher the percentage PEO, the higher the lubricity. Therefore, one may utilize a relatively higher percentage PEO composition on a catheter shaft and a relatively low percentage composition on the balloon to achieve the ends of this invention also i.e., xe2x80x9cdifferentialxe2x80x9d or xe2x80x9cselectivexe2x80x9d lubricity over a catheter. Of course, other compositions may also be utilized in this way.
Another embodiment comprises a coated catheter shaft, coated balloon cones and a coating on at least the distal waist of the balloon extending to the distal catheter tip, the balance of the balloon body having no coating or one of less lubricity.
In an additional embodiment, both the proximal and distal balloon cones are so coated similarly to the catheter shaft or at least the distal cone. In accordance with the invention, the balance of the balloon body is uncoated or coated with a relatively less lubricious coating.
In still a further embodiment, the balloon is partially or entirely coated with a tacky adhesive.
The advantage of the present invention is the ability to have a coated catheter which offers ease of movement through the vasculature along with the ability to effectively engage and deploy stents at any particular lesion without slippage or premature activation.